Adhesive sheet, dicing tape integrated type adhesive sheet, and method of producing semiconductor device

ABSTRACT

The invention provides an adhesive sheet which can be stuck to a wafer at low temperatures of 100° C. or below, which is soft to the extent that it can be handled at room temperature, and which can be cut simultaneously with a wafer under usual cutting conditions; a dicing tape integrated type adhesive sheet formed by lamination of the adhesive sheet and a dicing tape; and a method of producing a semiconductor device using them. In order to achieve this object, the invention is characterized by specifying the breaking strength, breaking elongation, and elastic modulus of the adhesive sheet in particular numerical ranges.

This application is a Divisional application of application Ser. No.10/559,684, filed Dec. 6, 2005, the contents of which are incorporatedherein by reference in their entirety. No. 10/559,684 is a NationalStage Application filed under 35 USC 371 of International (PCT)Application No. PCT/JP04/08150, filed Jun. 4, 2004.

TECHNICAL FIELD

The present invention relates to an adhesive sheet suitable for thejoint of a semiconductor element with a semiconductor-element-mountingsupport member, a dicing tape integrated type adhesive sheet, and amethod of producing a semiconductor device using them.

BACKGROUND ART

Hitherto, silver paste has been mainly used to joint a semiconductorelement with a semiconductor-element-mounting support member. However,the support member used has also been required to be made small-sizedand minute as semiconductors have been made small-sized and theperformance thereof has been made high in recent years. Silver paste hascome not to meet such requirements by generating of the problem at thetime of wire bonding resulting from the paste smudge and the inclinationof semiconductor elements, control difficulty of the film thickness ofan adhesive sheet, generating of voids in the adhesive sheet, andothers. In recent years, therefore, a sheet-form adhesive has come to beused in order to meet the requirements.

This adhesive sheet is used in an individual-piece sticking mode or awafer-back-face sticking mode. When the adhesive sheet in the formerindividual-piece sticking mode is used to produce a semiconductor, thesemiconductor device is obtained by cutting or punching out a reel-formadhesive sheet into individual pieces, bonding one out of the individualpieces onto a support member, jointing a semiconductor element made,through a dicing step, into an individual piece onto theadhesive-sheet-bonded support member to form asemiconductor-element-jointed support member, and, if necessary, causingthis member to undergo a wire bonding step, a sealing step and othersteps. However, in order to use the adhesive sheet in theindividual-piece sticking mode, it is necessary to use an exclusivefabricating device for cutting the adhesive sheet and then bonding theresultant onto the support member. Accordingly, there arises a problemthat costs for the production are higher than those in the method usingsilver paste.

Meanwhile, when the adhesive sheet in the wafer-back-face sticking modeis used to produce a semiconductor device, the semiconductor device isobtained by sticking the adhesive sheet onto the back face of asemiconductor wafer, sticking a dicing tape onto the other face of theadhesive sheet, dicing the wafer into individual semiconductor elements,picking up one of the individual adhesive-sheet-bonded semiconductorelements, jointing it with a support member, and causing the resultantto undergo the steps of heating, curing, wire bonding and others. Thisadhesive sheet in the wafer-back-face sticking mode does not require anydevice for making an adhesive sheet into individual pieces since asemiconductor element with the adhesive sheet is jointed with a supportmember. Thus, a conventional fabricating device for silver paste can beused as it is, or the device can be used in the state that a partthereof is improved by, for example, the addition of a hot platethereto. For this reason, attention is paid to the production method, asa method capable of making costs for the production relativelyinexpensive, among fabricating methods using an adhesive sheet.

However, in the method using an adhesive sheet in the wafer-back-facesticking mode, it is necessary to conduct two sticking steps, whereinthe adhesive sheet and a dicing tape are stuck, before theabove-mentioned dicing step. For this reason, there has been a requirefor simplified working steps. Thus, suggested is a method of putting anadhesive sheet onto a dicing tape, and sticking the resultant on a wafer(for example, Japanese Patent Application Laid-Open Nos. 2002-226796,2002-158276, and 2-32181).

In the method using an adhesive sheet in the wafer-back-face stickingmode, it is necessary to cut the adhesive sheet at the same time as awafer is diced. However, in ordinary dicing methods using a diamondblade, it is necessary to make the cutting speed small in order to cutthe wafer and the adhesive sheet simultaneously. Thus, costs increase.

In recent years, the following is suggested as a wafer-cutting method: amethod of performing the step of making a wafer into a state that thewafer can easily be cut, such as the step of making trenches which willbe cutting stripes in a wafer without being completely cut or the stepof forming a modified regions by radiating a laser into a wafer alonglines intended to be cut; and subsequently cutting the wafer by, forexample, the application of external force thereto. The former is calledhalf cut dicing, and the latter is called stealth dicing (for example,Japanese Patent Application Laid-Open Nos. 2002-192370 and 2003-338467).These methods have an advantageous effect of decreasing defects, such aschipping, when the thickness of a wafer is particularly small. Moreover,the methods require no calf width. Thus, according to the methods,yield-improving effect and other effects can be expected.

In order to perform a semiconductor device producing process accordingto the wafer-back-face sticking mode by use of the half cut dicing orstealth dicing, it is necessary to cut an adhesive sheet and a wafersimultaneously. However, when an ordinal adhesive sheet is used, it isdifficult to cut the sheet at the same time as a wafer is cut. When anon-elastic adhesive sheet having a good breakability is used as theadhesive sheet, the adhesive sheet and a wafer can be simultaneously cutin the state that cutting faces of the two are made substantiallyconsistent. However, the non-elastic adhesive sheet has a low fluidity;therefore, the sheet is not easily stuck onto the wafer at a lowtemperature of 100° C. or lower. Additionally, the adhesive sheet iscracked since the adhesive sheet itself is brittle. Thus, it is fearedthat adhesion reliability thereof deteriorates.

DISCLOSURE OF THE INVENTION

As described above, in the method using an adhesive sheet in thewafer-back-face sticking mode, no way of permitting a wafer and theadhesive sheet to be effectively cut has been found. Accordingly, in adicing step in the production of a semiconductor device, an adhesivesheet has been desired which can be cut at the same time as a wafer iscut after the work of the wafer into a cut-permissible state. Moreover,in the step of jointing a semiconductor element with a support member inthe production of a semiconductor device, an adhesive sheet which isexcellent in adhesion reliability has been desired.

An object of the present invention is to provide an adhesive sheet whichcan be stuck onto a wafer at low temperatures, is so flexible that thesheet can be handled at room temperature, and can be cut at the sametime as the wafer is cut under ordinary cutting conditions.

The inventors have found out that when the breaking strength and thebreaking elongation of an adhesive sheet in a B-stage state at 25° C.are restricted into specific numerical ranges, it is possible to obtainan adhesive sheet which can be cut at the same time as a wafer is cut atroom temperature.

Furthermore, the inventors have found out that in order for an adhesivesheet to keep flexibility at room temperature and be cut at the sametime as a wafer is cut at room temperature, it is necessary that theelastic modulus of the adhesive sheet has a specific frequencydependency. The frequency dependency is a phenomenon that a sample hasan elastic modulus variable in accordance with the frequency of a strainapplied to the sample in the measurement of the dynamic viscoelasticity.

Specifically, the present invention has, as it features, mattersdescribed in the following <1> to <15>:

<1> An adhesive sheet, comprising a polymer component, the breakingstrength of the adhesive sheet in a B-stage state being from 0.1 to 10MPa at 25° C., and the breaking elongation thereof being from 1 to 40%at 25° C.

<2> An adhesive sheet, comprising a polymer component, the elasticmodulus of the adhesive sheet in a B-stage state being from 1 to 3000MPa in measurement of the dynamic viscoelasticity at 25° C. and 10 Hz,and the elastic modulus thereof being from 4000 to 20000 MPa inmeasurement of the dynamic viscoelasticity at 25° C. and 900 Hz.

<3> An adhesive sheet, comprising a polymer component, the elasticmodulus of the adhesive sheet in a B-stage state being from 1 to 3000MPa in measurement of the dynamic viscoelasticity at 25° C. and 10 Hz,and the elastic modulus thereof being from 4000 to 20000 MPa inmeasurement of the dynamic viscoelasticity at −20° C. and 10 Hz.

<4> The adhesive sheet according to the above-mentioned <2> or <3>,comprising the polymer component, and the elastic modulus of theadhesive sheet in a B-stage state being from 0.1 to 20 MPa inmeasurement of the dynamic viscoelasticity at 60° C. and 10 Hz.

<5> The adhesive sheet according to any one of the above-mentioned <2>to <4>, comprising the polymer component, the breaking strength of theadhesive sheet in a B-stage state being from 0.1 to 10 MPa at 25° C.,and the breaking elongation thereof being from 1 to 40% at 25° C.

<6> The adhesive sheet according to any one of the above-mentioned <1>to <5>, wherein the polymer component has a glass transition temperatureof −30 to 50° C., and a weight-average molecular weight of 50000 to1000000.

<7> The adhesive sheet according to the above-mentioned <6>, wherein thepolymer component, which has a glass transition temperature of −30 to50° C. and a weight-average molecular weight of 50000 to 1000000, iscontained in an amount of 50% or less of the total weight of theadhesive sheet from which the weight of a filler is removed.

<8> The adhesive sheet according to the above-mentioned <7>, furthercomprising a thermosetting component.

<9> The adhesive sheet according to the above-mentioned <7> or <8>,further comprising 5 to 70% by weight of the filler.

<10> The adhesive sheet according to any one of the above-mentioned <1>to <9>, wherein the content of remaining volatile matters is from 0.01to 3% by weight.

<11> The adhesive sheet according to any one of the above-mentioned <1>to <10>, which has a film thickness of 1 to 250 μm.

<12> A dicing tape integrated type adhesive sheet formed by laminationof the adhesive sheet according to any one of the above-mentioned <1> to<11> and a dicing tape.

<13> A method of producing a semiconductor device, comprising: I) thestep of sticking the adhesive sheet according to any one of theabove-mentioned <1> to <11> onto a semiconductor wafer, II) the step ofrendering the semiconductor wafer permissible to be cut, III) the stepof sticking a dicing tape onto the adhesive sheet in order of I-II-III,II-I-III, or I-III-II, and further comprising: IV) the step of cuttingthe semiconductor wafer and the adhesive sheet, thereby yieldingadhesive-sheet-stuck semiconductor chips which are individual pieces,and V) the step of bonding the adhesive-sheet-stuck semiconductor chipsonto a semiconductor-chip-mounting support member.

<14> A method of producing a semiconductor device, comprising: I′) thestep of sticking the dicing tape integrated type adhesive sheetaccording to the above-mentioned <12> onto a semiconductor wafer, andII) the step of rendering the semiconductor wafer permissible to be cutin order of I′-II or II-I′, and further comprising: IV) the step ofcutting the semiconductor wafer and the adhesive sheet of the dicingtape integrated type adhesive sheet, thereby yieldingadhesive-sheet-stuck semiconductor chips which are individual pieces,and V) the step of bonding the adhesive-sheet-stuck semiconductor chipsonto a semiconductor-chip-mounting support member.

<15> The method of producing a semiconductor device according to theabove-mentioned <13> or <14>, wherein a method for rendering thesemiconductor wafer permissible to be cut is half cut dicing or stealthdicing.

The present application is an application with priority claims based onsome Japanese Patent Applications filed previously by the Applicant,that is, Japanese Patent Application No. 2003-161656 (filed on Jun. 6,2003) and Japanese Patent Application No. 2003-402748 (filed on Dec. 2,2003), Whose specifications are incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an embodiment of the step I) inthe invention.

FIG. 2 is a schematic view illustrating an embodiment of the step II) inthe invention.

FIG. 3 is a schematic view illustrating an embodiment of the step III)in the invention.

FIG. 4 is a schematic view illustrating an embodiment of the step IV) inthe invention.

FIG. 5 is a schematic view illustrating an embodiment of the step V) inthe invention.

FIG. 6 is a schematic view illustrating an embodiment of the step I′) inthe invention.

FIG. 7 is a schematic view illustrating an embodiment of the step II) inthe invention.

FIG. 8 is a schematic view illustrating a state that external force isapplied to a wafer in FIG. 7, whereby the wafer and an adhesive sheetare cut.

FIG. 9 is a schematic view illustrating an embodiment of the step V) inthe invention.

FIG. 10 is a schematic view illustrating an embodiment of anadhesive-sheet-stuck semiconductor chip.

FIG. 11 is a schematic view illustrating an embodiment of the steps I′),II) and IV) in the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The adhesive sheet of the present invention comprises a polymercomponent, and has the breaking strength in a B-stage state from 0.1 to10 MPa at 25° C., and the breaking elongation from 1 to 40% at 25° C.

If the breaking strength is less than 0.1 MPa, the adhesive sheet isbrittle and the handleability thereof deteriorates. If the breakingstrength is more than 10 MPa, the adhesive sheet cannot be cut at thesame time as a wafer is cut, which being inappropriate. Similarly, ifthe breaking elongation is less than 1%, the adhesive sheet is brittleand the handleability thereof deteriorates. If the breaking elongationis more than 40%, the adhesive sheet cannot be cut at the same time as awafer is cut, which being inappropriate. The breaking strength and thebreaking elongation are preferably from 1 to 8 MPa and from 5 to 35%,respectively, and are more preferably from 3 to 7 MPa and from 10 to30%, respectively, since the adhesive sheet can be surely broken whenthe wafer is broken and further the adhesive sheet has a sufficientstrength and an excellent handleability.

The breaking strength and the breaking elongation of the B-stage stateadhesive sheet at 25° C. are values obtained by using a tensile testerto measure the stress-strain curve of a sample having a width of 10 mm,a distance between chucks of 20 mm and a thickness of 5 to 250 μm at atensile speed of 0.5 m/minute and then making calculations in accordancewith the following equations:

Breaking strength (Pa)=Maximum strength (N)/Sectional area (m²) of thesample

Breaking elongation (%)=(Sample length (mm) when the sample isbroken−20)/20×100

In order to raise the breaking strength, it is effective to make theelastic modulus high and further make the toughness of the materiallarge. Specifically, it is effective to make the elastic modulus high bythe addition of various filler additives, and add a small amount ofrubber or the like in order to improve the toughness of the material. Inorder to decrease the breaking strength, it is effective to increase theadding amount of an oligomer and a monomer to decrease the breakingelongation of the film.

In order to raise the breaking elongation, it is effective to improvethe flexibility and the toughness of the material. For example, it iseffective to increase the amount of a polymer component having a low Tgand a large molecular weight and the adding amount of an oligomer and amonomer which each have a softening temperature lower than 30° C. Inorder to decrease the breaking elongation, it is effective to increasethe adding amount of an oligomer and a monomer which each have asoftening temperature of 30° C. or higher and the amount of a polymercomponent having a high Tg, and add a filler to lower the toughness.

The adhesive sheet of the present invention comprises a polymercomponent, and has the elastic modulus in a B-stage state from 1 to 3000MPa in measurement of the dynamic viscoelasticity at 25° C. and 10 Hz,and the elastic modulus from 4000 to 20000 MPa in measurement of thedynamic viscoelasticity at 25° C. and 900 Hz.

The elastic modulus at 25° C. and 10 Hz is preferably from 10 to 1500MPa, more preferably from 100 to 1200 MPa since the adhesive sheet isnot easily cracked when it is handled. If the elastic modulus is lessthan 1 MPa, the elongation of the adhesive sheet is large so that it isnot easily handled. If the elastic modulus is more than 3000 MPa, theadhesive sheet is cracked when it is handled, which are not preferable.The elastic modulus at 25° C. and 900 Hz is preferably from 5000 to15000 MPa. If the elastic modulus is less than 4000 MPa, the adhesivesheet tends not to be easily cut. If the elastic modulus is more than20000 MPa, the adhesive sheet tends to be easily cracked when it ishandled.

The adhesive sheet of the present invention comprises a polymercomponent, and has the elastic modulus in a B-stage state from 1 to 3000MPa in measurement of the dynamic viscoelasticity at 25° C. and 10 Hz,and the elastic modulus from 4000 to 20000 MPa in measurement of thedynamic viscoelasticity at −20° C. and 10 Hz.

The elastic modulus at −20° C. and 10 Hz is preferably from 5000 to15000 MPa. If the elastic modulus is less than 4000, the adhesive sheettends not to be easily cut. If it is more than 20000 MPa, the adhesivesheet tends to be easily cracked when it is handled.

It is sufficient that in any adhesive sheet of the invention, thevarious physical properties are within the above-specified ranges whenthe adhesive sheet is cut after the sheet is stuck onto a wafer. Thus,when the adhesive sheet is stuck, the physical properties may not bewithin the ranges. In other words, it is sufficient that the variousphysical properties are within the above-mentioned ranges after a givenstorage period from the time when the adhesive sheet is stuck onto awafer or after the adhesive sheet undergoes working of thermal treatmentor radial ray radiation such as optical curing. For example, in the caseof using an adhesive sheet having a large breaking strength and a largebreaking elongation before the sheet is stuck onto a semiconductorwafer, the adhesive sheet can be stuck onto the semiconductor wafer at alow temperature. The breakability can be improved by setting thebreaking strength and the breaking elongation within the above-mentionedranges after the adhesive sheet is stuck. Similarly, even if the elasticmodulus of an adhesive sheet at 25° C. and 10 Hz is less than 1 MPa atan initial stage, the adhesive sheet has intense adhesive property andcan easily be laminated at room temperature when the adhesive sheet isstuck onto a wafer. Thereafter, the elastic modulus is set into theabove-mentioned range, whereby the breakability can be improved.

When the adhesive sheet of the present invention is used, it ispreferred to laminate the sheet onto a wafer at a temperature from 40 to100° C. in order to make a warp of the wafer small and make thehandleability good at room temperature. For this purpose, as for theadhesive sheet of the present invention, the elastic modulus of theadhesive sheet in a B-stage state is preferably from 0.1 to 20 MPa, morepreferably from 0.1 to 10 MPa, and in particular preferably from 0.1 to5 MPa in measurement of the dynamic viscoelasticity at 60° C. and 10 Hz.If the elastic modulus is less than 0.1 MPa, the sheet may be peeled orshifted from a wafer after the sheet is stuck thereto, which is notpreferred.

The adhesive sheet of the present invention preferably has theabove-mentioned various properties as well as heat resistance andhumidity resistance required when a semiconductor element is mountedonto a semiconductor-element-mounting support member.

Especial limitation is not imposed on the adhesive sheet of the presentinvention if the adhesive sheet satisfies the above-mentionedproperties. It is preferred that the adhesive sheet contains athermosetting component and a filler besides the polymer component sincethe adhesive sheet has an appropriate tacking strength and a goodhandleability in a sheet form. The adhesive sheet may contain,additionally, a curing accelerator, a catalyst, an additive, a couplingagent, and so on. The breaking strength and the breaking elongation tendto become higher as the amount of the polymer component contained in theadhesive sheet is larger and the amount of the filler is smaller; it istherefore important to adjust these components such that the breakingstrength and the breaking elongation are set within the numerical rangesspecified in the present invention.

The following will describe the components which constitute any adhesivesheet of the present invention in more detail.

The polymer component in the present invention is not particularlylimited as long as the component causes the properties of the adhesivesheet to be satisfied. Preferably, the glass transition temperature(abbreviated to Tg hereinafter) thereof is from −30 to 50° C. and theweight-average molecular weight is from 50000 to 1000000. If the Tg ishigher than 50° C., the flexibility of the sheet is inconveniently low.If the Tg is lower than −30° C., the flexibility of the sheet is toohigh. Thus, it is not convenient since the sheet is not easily brokenwhen the wafer thereon is broken. If the weight-average molecular weightis less than 50000, the heat resistance of the sheet lowersinconveniently. If the molecular weight is more than 1000000, thefluidity of the sheet lowers inconveniently.

From the viewpoint of the breakability and the heat resistance of theadhesive sheet when the wafer thereon is cut, the Tg and theweight-average molecular weight are more preferably from −20 to 40° C.and from 100000 to 900000, respectively, preferably from −10 to 50° C.and from 50000 to 1000000, respectively, and in particular preferablyfrom −10 to 30° C. and from 500000 to 900000, respectively. Theweight-average molecular weight is a value in terms of polystyrene onthe basis of gel permeation chromatography (GPC) using a calibrationcurve of standard polystyrene, and was measured by using an L-6000(trade name) manufactured by Hitachi Ltd. as a pump, a column wherein aGel pack GL-R440, a Gelpack GL-R450 and a Gelpack GL-R400M (each 10.7 mmdiameter×300 mm) manufactured by Hitachi Chemical Co., Ltd. areconnected in this order as a column, and tetrahydrofuran as an eluent,and measuring a sample wherein 120 mg of a specimen was dissolved in 5mL of THF at a flow rate of 1.75 mL/minute.

Specific examples of the polymer component include polyimide,polystyrene, polyethylene, polyester, polyamide, butadiene rubber,acrylic rubber, (meth) acrylic resin, urethane resin, polyphenyleneether resin, polyetherimide resin, phenoxy resin, modified polyphenyleneether resin, phenoxy resin, polycarbonate, and mixtures thereof.Particularly preferred is a polymer component containing a functionalmonomer and having a weight-average molecular weight of 100000 or more,for example, an epoxy group-containing (meth) acrylic copolymercontaining a functional monomer, such as glycidyl acrylate or glycidylmethacrylate, and further having a weight-average molecular weight of100000. As the epoxy group-containing (meth)acrylic copolymer, forexample, (meth) acrylic ester copolymer, acrylic rubber or the like canbe used. Acrylic rubber is more preferred. Acrylic rubber is a rubberwhich contains an acrylic acid ester as a main component and is mademainly of a copolymer made of butyl acrylate, acrylonitrile and others,or a copolymer made of ethyl acrylate, acrylonitrile and others.

The polymer component is contained preferably in an amount of 50% orless of the total weight of the adhesive sheet from which the weight ofthe filler is removed, more preferably in an amount of 35% or less, andin particular preferably in an amount from 25 to 35%. If the blendamount of the polymer component is large, the breakability of theadhesive sheet tends to deteriorate. If the blend amount is small, thefluidity is too large when the sheet is bonded so that voids tend to begenerated.

Examples of the thermosetting component include epoxy resin, cyanateresin, phenol resin, and cured products thereof. Epoxy resin ispreferred since the resin has a high heat resistance. The epoxy resin isnot particularly limited as long as the resin has adhesive effect whenit is cured. The following can be used: a bifunctional epoxy resin suchas bisphenol A type epoxy; a novolak epoxy resin such as phenol novolakepoxy resin or cresol novolak epoxy resin; or the like. Moreover, anordinarily-known epoxy resin can be used, examples of which includepolyfunctional epoxy resin, glycidylamine epoxy resin,heteroring-containing epoxy resin, or alicyclic epoxy resin.

It is preferred to incorporate a filler, preferably an inorganic fillerinto the adhesive sheet of the invention in order to decrease thebreaking strength and the breaking elongation of the adhesive sheet in aB-stage state, improve the handleability and thermal conductivity of theadhesive, adjust the melting viscosity, and give thixotropy.

Examples of the inorganic filler include aluminum hydroxide, magnesiumhydroxide, calcium carbonate, magnesium carbonate, calcium silicate,magnesium silicate, calcium oxide, magnesium oxide, alumina, aluminumnitride, aluminum borate whisker, boron nitride, crystalline silica,amorphous silica, and antimony oxide. In order to improve the thermalconductivity, preferred are alumina, aluminum nitride, boron nitride,crystalline silica, amorphous silica, and so on. In order to adjust themelting viscosity and give thixotropy, preferred are aluminum hydroxide,magnesium hydroxide, calcium carbonate, magnesium carbonate, calciumsilicate, magnesium silicate, calcium oxide, magnesium oxide, alumina,crystalline silica, amorphous silica, and so on. In order to improve thehumidity resistance, preferred are alumina, silica, aluminum hydroxide,and antimony oxide.

The amount of the filler is preferably from 5 to 70% by weight of thetotal of the adhesive sheet, more preferably from 35 to 60% by weight.If the blend amount thereof is large, there are easily caused problems,such as a rise in the storage elastic modulus of the adhesive sheet, afall in the adhesive property thereof, and a deterioration in theelectrical properties due to remaining voids. Thus, the amount is inparticular preferably set to 50% or less by weight. The specific gravityof the filler is preferably from 1 to 10 g/cm³.

The adhesive sheet of the invention may contain an acrylic monomerhaving in the molecule thereof one or more unsaturated double bonds anda photoinitiator therefor, thereby having UV curability. When theadhesive sheet is laminated at a low temperature and then the breakingelongation thereof is lowered by the irradiation with UV, thebreakability can be improved.

The adhesive sheet of the invention can be obtained by mixing andkneading the above-mentioned polymer component and the optionalthermosetting component, filler and other components in an organicsolvent to prepare a varnish, forming a layer of the varnish on asubstrate film, heating and drying the layer, and then removing thesubstrate.

The above-mentioned mixing and kneading can be performed by means of anappropriate combination of two or more ordinary dispersers such as astirrer, a crusher, a three-axis roll, and a ball mill. Conditions forthe above-mentioned heating and drying are not particularly limited aslong as the conditions are conditions for volatilizing the used solventsufficiently. Usually, the vanish layer is heated at 60 to 200° C. for0.1 to 90 minutes.

The organic solvent used in the preparation of the varnish in theproduction of the adhesive sheet is not particularly limited as long asthe solvent is an organic solvent which makes it possible to dissolve,knead and disperse the materials evenly, and the solvent may be onewhich is known in the art. Examples of such a solvent includedimethylformamide, dimethylacetoamide, N-methylpyrrolidone, ketonesolvents such as acetone, methyl ethyl ketone and cyclohexanone,toluene, and xylene. Methyl ethyl ketone, cyclohexanone or the like ispreferably used since it has a high drying rate and it is inexpensive.

The amount of the used organic solvent is not particularly limited aslong as the remaining volatile matter content is from 0.01 to 3% byweight of the whole after the adhesive sheet is produced. From theviewpoint of heat-resistant reliability, the content is preferably from0.01 to 2.0% by weight, more preferably from 0.01 to 1.5% by weight ofthe whole.

Plural bodies of any adhesive sheet of the invention may be stacked ontoeach other to produce a multi-layered adhesive sheet as long as they canbe cut. A multi-layered adhesive sheet may be produced by combining anyadhesive sheet of the present invention with a film made of athermoplastic film, an adhesive, a thermosetting resin and so on andlaminating two bodies of the adhesive sheet on both faces of the film.The wording “as long as they can be cut” means that the breakingstrength and the breaking elongation of the multi-layered sheet arewithin the above-mentioned numerical ranges. Such a film is, forexample, a film made of a thermoplastic resin such as polyimide orpolyester, an epoxy resin, a silicon resin, or a mixture thereof. Thefilm may contain various fillers.

The film thickness of any adhesive sheet of the invention is notparticularly limited, and is preferably from 1 to 250 μm. If thethickness is smaller than 1 μm, the stress-relaxing effect and theadhesive property thereof tend to become poor. If the thickness islarger than 250 μm, economical disadvantages are generated. Furthermore,a requirement of making a semiconductor device small-sized is not metand the adhesive sheet tends not to be easily broken. The thickness ispreferably from 3 to 100 μm, more preferably from 5 to 55 μm since ahigh adhesive property is given and a semiconductor device can be madesmall-sized.

The dicing tape integrated type adhesive sheet of the present inventioncan be obtained by laminating any adhesive sheet of the presentinvention on a known dicing tape. When this dicing tape integrated typeadhesive sheet is used, only a single step of lamination onto a wafer isrequired and the work can be made effective. The method for laminatingthe adhesive sheet onto the dicing tape may be, for example, a method ofpressing or hot-roll-laminating the adhesive sheet formed in advanceonto the dicing tape besides printing. Preferred is thehot-roll-laminating method since the dicing tape integrated typeadhesive sheet can be continuously produced and the efficiency of themethod is good.

Examples of the dicing tape used in the invention include apolytetrafluoroethylene film, a polyethylene terephthalate film, apolyethylene film, a polypropylene film, a polymethylpentene film, apolyimide film, and other plastic films. If necessary, the dicing tapemay be subjected to a surface treatment such as primer painting, UVtreatment, corona discharge treatment, polishing treatment, or etchingtreatment. The dicing tape needs to have adhesiveness. An adhesive layermay be formed on a single face of the dicing tape. This can be formed bypainting and drying a resin composition, for the adhesive layer, havingan appropriate tacking strength obtained by adjusting, in particular,the ratio between liquid components therein, or the Tg of the polymercomponent therein.

The film thickness of the dicing tape is not particularly limited, andis appropriately decided on the basis of knowledge of those skilled inthe art in accordance with the film thickness of the adhesive sheet orthe usage of the dicing tape integrated type adhesive sheet. The filmthickness is from 60 to 150 μm, preferably from 70 to 130 μm sinceeconomical advantages are given and the handleability of the film isgood.

It is necessary that any adhesive sheet of the present invention or theadhesive sheet of the dicing tape integrated type adhesive sheet of theinvention has such an adhesive force that semiconductor elements are notscattered at the time of dicing in the production of a semiconductordevice and can be peeled from the dicing tape at the time of picking-upsubsequent thereto. For example, if the adhesiveness of the adhesivesheet or the dicing tape is too high, the resin in terminal regions ofthe trenches melts so that the separation thereof becomes difficult.Therefore, the 90° peel strength between the adhesive sheet of theinvention and a dicing tape thereon in a B-stage state is preferably 150N/m or less, more preferably from 5 to 100 N/m, and even more preferablyfrom 5 to 50 N/m. If the peel strength is more than 150 N/m, chips tendto be easily cracked at the time of the picking-up. The peel strength isa result obtained when the adhesive sheet is peeled from the dicing tapeat an angle of 90° and a tensile speed of 50 mm/minute in an atmosphereof 25° C. temperature.

In order to set the 90° peel strength to 150 N/m or less, it is desiredto adjust the tacking strength of the adhesive sheet appropriately. Itis advisable to perform the method for adjusting the tacking strength byuse of a nature that: when the fluidity of the adhesive sheet is raisedat room temperature, the adhesive force and the tacking strength tend torise; and when the fluidity is lowered, the adhesive force and thetacking strength tend to fall. For example, to raise the fluidity,methods such as an increase in the content of a plasticizer, an increasein the content of a tackifier, or some other methods are adopted.Conversely, to lower the fluidity, the content of above-mentionedcompound is decreased. Examples of the plasticizer include amonofunctional acrylic monomer, a monofunctional epoxy resin, a liquidepoxy resin, an acrylic resin, and what is called a diluting agent of anepoxy type.

A semiconductor device can be produced by use of any adhesive sheet ofthe present invention or a dicing tape integrated type adhesive sheethaving any adhesive sheet of the invention.

Specifically, a method of producing the semiconductor of the inventioncomprises: I) the step of sticking any adhesive sheet of the inventiononto a semiconductor wafer, II) the step of rendering the semiconductorwafer permissible to be cut, III) the step of sticking a dicing tapeonto the adhesive sheet of the invention in order of I-II-III, II-I-III,or I-III-II, and further comprises: IV) the step of cutting thesemiconductor wafer and the adhesive sheet, thereby yieldingadhesive-sheet-stuck semiconductor chips which are individual pieces,and V) the step of bonding the adhesive-sheet-stuck semiconductor chipsonto a semiconductor-chip-mounting support member.

FIG. 1 illustrates an embodiment of the step of sticking an adhesivesheet 1 of the present invention onto a semiconductor wafer A; FIG. 2illustrates that of the step of radiating a laser ray onto lines alongwhich the semiconductor wafer A is to be cut, thereby forming modifiedregions (cutting-intended regions) 5 inside the wafer to render thewafer permissible to be cut; FIG. 3 illustrates that of the step ofsticking a dicing tape 2 composed of an adhesive layer 2 a and asubstrate layer 2 b onto the adhesive sheet 1; FIG. 4 illustrates thatof the step of expanding the dicing tape 2, thereby cutting thesemiconductor wafer A and the adhesive sheet 1; and FIG. 5 illustratesthat of the step of bonding an adhesive-sheet-stuck semiconductor chip 6onto a semiconductor-chip-mounting support member 7.

The semiconductor wafer is made of one or more selected from polycrystalsilicon, various ceramics, and compound semiconductors, such as galliumarsenic, besides monocrystal silicon.

The temperature at which the adhesive sheet is stuck onto the wafer inthe step I), that is, the laminating temperature is preferably from 0 to170° C. In order to make a warp of the wafer small, the temperature ismore preferably from 20 to 130° C., in particular preferably from 20 to60° C. When the step I) is performed after the step II), it is preferredto perform the lamination while the wafer is supported not to bedeformed in order to prevent the wafer from being broken by stress ordeformation in the laminating step.

The working method for rendering the wafer permissible to be cut in thestep II) may be a method of rendering the wafer which will be able to beeasily cut by subsequent application of external force thereto. Forexample, a method of making trenches which will be cutting stripeswithout cutting the wafer completely into chips with a dicing cutter orthe like or a method of radiating a laser ray into a wafer along linesintended to be cut, thereby forming modified regions, etc. can bementioned. About the laser processing of the wafer, methods described inJapanese Patent Application Laid-Open Nos. 2002-192370 and 2003-338467can be used. About the machine therefor, for example, a MAHOHDICINGMACHINE manufactured by Tokyo Seimitsu Co., Ltd. can be used. The laserray into the semiconductor wafer may be radiated through the front faceof the semiconductor wafer, that is, the face on which a circuit isformed, or may be radiated through the rear face of the semiconductorwafer, that is, the face on which no circuit is formed and the adhesivesheet is stuck. In the case that the step II) is performed after thestep I), the step I′) which will be described later, or the step III, itis preferred to use, as the adhesive sheet or the dicing tape, a sheetor a tape which transmits the laser ray since the laser ray thereby canbe radiated into the semiconductor wafer from the side of the adhesivesheet or the dicing tape. It is also preferred that the adhesive sheethas a different transparency or color tone from that of the dicing tapesince its portion that has been unable to be broken, that is, be cut iseasily recognized.

In the present invention, for example, the above-mentioned laserprocessing machine is used to focus a ray on an inner portion of thesilicon wafer, and the laser ray is radiated thereto from the side ofthe front face of the silicon wafer along its lines intended to be cut,under conditions described below. In this way, modified regions areformed inside the silicon wafer. Wafers can be cut according to themodified regions along the lines intended to be cut. The modifiedregions are preferably melting-treated regions formed by heating andmelting the inner regions of the semiconductor wafer locally bymulti-photons absorption.

(Laser Processing Conditions)

-   (A) Semiconductor substrate: a silicon wafer (thickness: 350 μm, and    outer diameter: 6 inches)-   (B) Laser source: a semiconductor laser excitation Nd:YAG laser

Wavelength: 1064 nm

Laser ray spot sectional area: 3.14×10⁻⁸ cm²

Oscillation mode: Q switch pulse

Recurring frequency: 100 kHz

Pulse width: 30 ns

Power: 20 μJ/pulse

Laser ray quality: TEM₀₀

Polarization property: linearly polarized light

-   (C) Condensing Laser

Magnification: 50 times

NA: 0.55

Transmittance to the laser ray wavelength: 60%

-   (D) Shifting speed of a mounting support on which the semiconductor    substrate is put: 100 mm/second

In the step III), the dicing tape is stuck onto the face opposite to theface of the semiconductor wafer onto which the adhesive sheet is stuckby a method known in the prior art. The temperature for the sticking,that is, the laminating temperature is preferably from 0 to 60° C., morepreferably from 10 to 40° C., and even more preferably from 15 to 30° C.In the case that the step III) is performed after the step II), it ispreferred to perform the lamination while supporting the wafer not to bedeformed in order to prevent the wafer from being broken by stress ordeformation in the laminating step.

The semiconductor producing method of the present invention maycomprise, as the step I′) instead of the steps I) and III), the step ofsticking a dicing tape integrated type adhesive sheet of the inventiononto the semiconductor wafer.

In this case, the method of producing a semiconductor device of thepresent invention comprises I′) the step of sticking a dicing tapeintegrated type adhesive sheet of the invention onto a semiconductorwafer, and II) the step of rendering the semiconductor wafer permissibleto be cut in order of I′-II or II-I′,

and further comprises: IV) the step of cutting the semiconductor waferand the adhesive sheet of the dicing tape integrated type adhesive sheetof the invention, thereby yielding adhesive-sheet-stuck semiconductorchips which are individual pieces, and V) the step of bonding theadhesive-sheet-stuck semiconductor chips onto asemiconductor-chip-mounting support member.

FIG. 6 illustrates one embodiment of the step of sticking a dicing tapeintegrated type adhesive sheet 3 of the present invention onto asemiconductor wafer A; FIG. 7 illustrates that of the step ofhalf-cutting the semiconductor wafer A with a dicing saw to render thewafer A permissible to be cut; FIG. 8 illustrates that of the state thatexternal force is applied to the dicing tape integrated type adhesivesheet 3, whereby the wafer A and the adhesive sheet 1 of the dicing tapeintegrated type adhesive sheet 3 are cut; and FIG. 9 illustrates that ofthe step of bonding an adhesive-sheet-stuck semiconductor chip 6 onto asemiconductor-chip-mounting support member 7. FIG. 11 illustrates thefollowing steps together: the step of sticking the dicing tapeintegrated type adhesive sheet 3 of the invention onto the semiconductorwafer A, the step of radiating a laser ray onto lines intended to be cutin the semiconductor wafer A so as to form modified regions(cutting-intended regions) 5 inside the wafer 5, thereby rendering thewafer permissible to be cut, and the step of applying external force tothe dicing tape 2 or the dicing tape integrated type adhesive sheet 3,thereby cutting the semiconductor wafer A and the adhesive sheet 1. Inthe method of producing a semiconductor device of the invention, thecombination of the method for sticking the adhesive sheet and the dicingtape onto the wafer with the dicing method is not particularly limited.From the viewpoint of workability and efficiency, a combination of thesticking of the dicing tape integrated type adhesive sheet of theinvention onto the wafer with stealth dicing is most preferred.

When the dicing tape integrated type adhesive sheet is stuck onto thesemiconductor wafer, they are stuck on each other so as to bring thesemiconductor wafer into contact with the adhesive sheet face of thedicing tape integrated type adhesive sheet. The temperature for thesticking, that is, the laminating temperature is preferably from 0 to170° C. In order to make a warp of the wafer small, the temperature ismore preferably from 20 to 130° C., in particular preferably from 20 to60° C.

After the steps I), II) and III), or the step I′) and II), the step IV)is performed; in this step, the cutting of the semiconductor wafer andthe adhesive sheet can be attained by applying external force to thedicing tape or the dicing tape integrated type adhesive sheet. Forexample, in the case of half cut dicing, this external force ispreferably applied thereto in a bending direction or twisting direction.In the case of stealth dicing, the force is preferably applied theretoin an expanding direction.

For example, in the case of expanding both ends of the dicing tape instealth dicing to apply external force, thereby cutting the wafer andthe adhesive sheet, the cutting can be attained with a commerciallyavailable wafer expanding device. More specifically, as illustrated inFIG. 4, a ring 11 is stuck and fixed onto the periphery of the dicingtape 2 arranged on a stage 13, and next a pushing-up section 12 israised to apply tensile force the dicing tape 2 from its both ends. Thespeed of raising the pushing-up section at this time is defined as theexpand speed and the height 14 of the elevation of the pushing-upsection is defined as the expand amount. In this case, the expand speedis preferably from 10 to 1000 mm/second, more preferably from 10 to 100mm/second, and in particular preferably from 10 to 50 mm/second in theinvention. The expand amount is preferably from 5 to 30 mm, morepreferably from 10 to 30 mm, and in particular preferably from 15 to 20mm. If the expand speed is less than 10 mm/second, the semiconductorwafer and the adhesive sheet tend not to be easily cut. If the speed ismore than 1000 mm/second, the dicing tape tends to be easily broken. Ifthe expand amount is less than 5 mm, the semiconductor wafer and theadhesive sheet tend not to be easily cut. If the amount is more than 30mm, the dicing tape tends to be easily broken.

When the dicing tape is expanded in this way so as to apply externalforce, the semiconductor wafer is cracked in the thickness directionthereof from the modified regions, inside the wafer, as starting points.This crack reaches the front and rear faces of the wafer and the rearface of the adhesive sheet adhering closely to the semiconductor wafer.Thus, the semiconductor wafer and the adhesive sheet are broken, thatis, are cut. In this way, adhesive-sheet-stuck semiconductor chips canbe obtained.

When the expand amount is more than 25 mm, it is preferred to use avinyl chloride base material for the substrate layer of the dicing tape.If the amount of the expand is small, it is preferred to use variouspolyolefin base materials. Preferably, the expand is performed at roomtemperature. As the need arises, the temperature for the expand may beadjusted in the range of −50 to 100° C. In the invention, thetemperature is preferably from −50 to 60° C., more preferably form 0 to40° C. As the temperature at the time of the expand is lower, thebreaking elongation of the adhesive sheet is smaller so as to be moreeasily be cut. Accordingly, lower temperature is more preferred in orderto prevent a decline in the yield due to the cut failure of the adhesivesheet.

In the case that a UV curing adhesive agent is used in the adhesivelayer of the dicing tape, ultraviolet rays are radiated to the dicingtape from the side of its face opposite to its semiconductor-wafer-stuckface before or after the expand, so as to cure the UV curing adhesiveagent. In this way, the adhesive force between the UV curing adhesiveagent and the adhesive sheet lowers, thereby making picking-up in thesubsequent step V) easy.

Subsequently, in the step V), an adsorbing collet 21, a needle clamp 22and so on, as illustrated in FIG. 5 or 9, are used as picking-up meansto pick up a number of the adhesive-sheet-stuck semiconductor chips,which are individual pieces, and this is mounted onto asemiconductor-chip-mounting area of a semiconductor-chip-mountingsupport member. The adhesive sheet is then heated and cured. Usually,the heating and curing are performed at a temperature ranging from 100to 220° C.

The semiconductor producing method of the invention is not limited tothe above-mentioned processes, and may comprise any other step. Forexample, in any stage after the step I) or I′) is performed and beforethe step IV) is performed, the method may comprise the step of radiatingultraviolet rays, infrared rays or microwaves into the adhesive sheet,or the step of heating or cooling the adhesive sheet. If necessary, themethod comprises a wire bonding step, a sealing step or the like afterthe step V) is performed.

EXAMPLES

The present invention will be described in more detail by way of thefollowing examples. However, the invention is not limited thereto.

[Compositions of Adhesive Sheets, and Producing Method Thereof] Example1

Cyclohexanone was added to a composition composed of: 30 parts by weightof a bisphenol F type epoxy resin (trade name: YD-8170C, manufactured byTohto Kasei Co., Ltd., epoxy equivalent: 160) and 10 parts by weight ofa cresol novolak type epoxy resin (trade name: YDCN-703, manufactured byTohto Kasei Co., Ltd., epoxy equivalent: 210) as epoxy resins; 27 partsby weight of a phenol novolak resin (trade name: Priophen LF2882,manufactured by Dainippon Ink & Chemicals, Inc.) as a curing agent forthe epoxy resins; 28 parts by weight of an epoxy-group-containingacrylic rubber (trade name: HTR-860P-3DR, manufactured by Nagase ChemtexCorp.; weight-average molecular weight based on gel permeationchromatography: 800000, glycidyl methacrylate: 3% by weight, and Tg: −7°C.) as an epoxy-group-containing acrylic copolymer; 0.1 part by weightof an imidazole curing accelerator (Curezol, manufactured by ShikokuChemicals Corp.) as a curing accelerator; 95 parts by weight of a silicafiller (S0-C2 (specific gravity: 2.2 g/cm³), manufactured by AdmafineCorp.); and 0.25 part by weight of a silane coupling agent (trade name:A-189, manufactured by Nippon Unicar Company Limited) and 0.5 part byweight of a silane coupling agent (trade name: A-1160 manufactured byNippon Unicar Company Limited). The components were stirred, mixed andsubjected to vacuum deairing to yield an adhesive agent varnish.

This adhesive agent varnish was applied onto a polyethyleneterephthalate film, 50 μm in thickness, subjected to releasingtreatment, and then the resultant was heated and dried at 90° C. for 10minutes and at 120° C. for 5 minutes to give a coating film 25 μm inthickness. In this way, an adhesive sheet in a B-stage state wasproduced. In the same manner, an adhesive sheet, 75 μm in thickness, ina B-stage state was produced.

Examples 2 to 6

About respective compositions shown in Table 1, adhesive sheets wereproduced in the same way as in Example 1. The adhesive sheet of Example6 was an adhesive sheet obtained by subjecting the sheet of Example 1 toheat treatment at 40° C. for 24 hours, thereby lowering the breakingelongation.

Comparative Examples 1 to 5

About respective compositions shown in Table 1, adhesive sheets wereproduced in the same way as in Example 1.

TABLE 1 Com- Com- Com- Com- Com- para- para- para- para- para- tive tivetive tive tive Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- ample ampleample ample ample ample ample ample ample ample ample Items Unit 1 2 3 45 6 1 2 3 4 5 YD-8170C Parts 30 30 30 30 30 30 30 30 30 30 30 by weightYDCN-703 Parts 10 10 10 10 10 10 10 10 10 10 10 by weight LF-2882 Parts27 27 27 27 27 27 27 27 27 27 27 by weight 2PZ-CN Parts 0.1 0.1 0.1 0.10.1 0.1 0.1 0.1 0.1 0.1 0.1 by weight A-189 Parts 0.25 0.25 0.25 0.250.25 0.25 0.25 0.25 0.25 0.25 0.25 by weight A-1160 Parts 0.5 0.5 0.50.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 by weight HTR-860P-3 Parts 28 44.1 33.131.7 28.3 28.0 180 28.3 66.1 44.1 66.1 by weight SO-C2 Parts 95 110 66.1132.2 180.6 95 0 0 253 47.2 56.7 by weight Polymer % 29.2 39.4 32.8 31.829.4 29.2 72.6 29.4 49.3 39.4 49.3 fraction * Filler % 49.8 49.6 39.657.0 65.3 49.8 0 0 65.4 29.7 29.7 weight fraction Filler % 34.1 34.025.5 40.9 49.6 34.1 0 0 49.7 18.1 18.1 volume fraction * Polymerfraction: the weight fraction of polymer components having a Tg from −10to 50° C. and a weight-average molecular weight from 50000 to 1000000 toall constituent components of each adhesive sheet from which any fillercomponent was removed

Among the adhesive sheets of Examples 1 to 6 and Comparative Examples 1to 5, the adhesive sheets 75 μm in thickness were used to makeevaluation about elastic modulus out of the following evaluation items,and the adhesive sheet 25 μm in thickness were used to make evaluationabout other items. The resultant results are shown in Table 2.

[Adhesive Sheet Evaluating Method] (1) Breaking Strength and BreakingElongation

About each of the samples of the B-stage state adhesive sheets having awidth of 10 mm, a length of 30 mm and a thickness of 25 μm, a tensiletester (a digital load indicator manufactured by Imada Corp.) was usedto measure the stress-strain curve thereof at a distance between itschuck of 20 mm and a tensile speed of 0.5 m/minute, and then thebreaking strength and breaking elongation thereof at 25° C. wereobtained therefrom in accordance with the following equations:

Breaking strength (Pa)=Maximum strength (N)/Sectional area (m²) of thesample

Breaking elongation (%)=(Sample length (mm) between the chucks when thesample was broken−20)/20×100

(2) Remaining Volatile Matter Content

The remaining volatile matter content was obtained by measuring theweight (mass A) of each of the B-stage state films, which was cut into a5 cm square, allowing the film to stand still on a releasable substratein a drying machine at 170° C. for 1 hour, measuring the weight (mass B)thereof again, and then making a calculation in accordance with thefollowing equation:

Remaining volatile matter content (%)=(A−B)×100/A

(3) Elastic Modulus (Storage Elastic Modulus)

A dynamic viscoelasticity measuring device (DVE-V4, manufactured byRheology Co.) was used to measure the storage elastic modulus of each ofthe B-stage state adhesive sheets (sample size: 20 mm in length×4 mm inwidth×74 μm in thickness, temperature range: −30 to 100° C.,temperature-raising rate: 5° C./minute, and tensile mode: 10 Hz or 900Hz under an automatic static load).

(4) Tacking Strength

A tacking tester manufactured by Rhesca Company, Limited was used tomeasure the tacking strength of each of the B-stage state adhesivesheets at 25° C. in accordance with a method described in JISZ0237-1991(probe diameter: 5.1 mm, peeling speed: 10 mm/s, contact load: 100gf/cm², and contact time: 1 second).

(5) Adhesive Force

A chip (5 mm square) and a gold plating substrate (a copper foil fittedflexible substrate electroplated with gold (Ni: 5 μm, and Au: 0.3 μm))were laminated onto each of the adhesive sheets on a hot plate of 120°C. temperature, and then the sheet was cured at 130° C. for 30 minutesand at 170° C. for 1 hour. About this sample, the peel strength thereofwas measured at 260° C. before the sample absorbed moisture and afterthe sample absorbed moisture at 85° C./85% RH for 48 hours.

(6) Laminate Property

Each of the adhesive sheets having a width of 10 mm and a wafer werelaminated onto each other with a hot roll laminator (at 60° C., 0.3m/minute and 0.3 MPa). Thereafter, a UTM-4-100 model tensilonmanufactured by Toyobalwin was used to peel the adhesive sheet at anangle of 90° and a tensile speed of 50 mm/minute in an atmosphere of 25°C. temperature. The peel strength at this time was obtained. In the casethat the adhesive sheet had a peel strength of 30 N/m or more, thelaminate property was judged to be good. In the case that the adhesivesheet had a peel strength of less than 30 N/m, the laminate property wasjudged to be poor.

(7) Flow

By use of a thermo-compression bonding tester (manufactured by TesterSangyo Co., Ltd.), a sample obtained by punching out each of the samplesand a PET film thereon into the form of a 1×2 cm stripe was pressed at ahot plate temperature of 160° C. and a pressure of 1 MPa for 18 seconds.Thereafter, the length of the resin forced out from the edge of thesample was measured with an optical microscope. This was defined as theflow amount.

(8) Breakability by Half-cut Dicing

An adhesive sheet and a dicing tape, which were separately produced,were arranged in such a manner that the adhesive sheet was stacked ontothe dicing tape. These were laminated on each other at 25° C. with a hotroll laminator (Riston manufactured by Du Pont), thereby yielding adicing tape integrated type adhesive sheet. At this time, the useddicing tape was a dicing tape (UC3004M-80) manufactured by the FurukawaElectric Co., Ltd. The film thickness of the dicing tape was 80 μm.Next, a semiconductor wafer to be diced was stuck onto the adhesivesheet face of the dicing tape integrated type adhesive sheet. At thistime, the used semiconductor wafer was a semiconductor wafer having athickness of 80 μm. The laminating temperature was 60° C. Subsequently,a dicing cutter was used to half-cut-dice the wafer, and then washed anddried to work the wafer into a cut-permissible state, so that at leasttwo semiconductor chips would be yielded when external force was appliedto the wafer. Thereafter, the dicing tape integrated type adhesive sheetwas bent, thereby cutting the adhesive sheet and the semiconductor waferto yield adhesive-sheet-stuck semiconductor chips. If the semiconductorwafer and the adhesive sheet were simultaneously cut by 90% or more ofthe distance over which they were half-cut-diced, the breakabilitythereof was judged to be good. If they were simultaneously cut by lessthan 90% thereof, the breakability was judged to be poor.

(9) Reflow Crack Resistance, and Temperature Cycle Resistance

A semiconductor element and each of the adhesive sheets, which were eachcut into a 5 mm square, were laminated onto a wiring board wherein apolyimide film 25 μm in thickness was used as its substrate. In thisway, semiconductor device samples (wherein solder balls were formed ontheir single face) were produced. The heat resistance thereof wasexamined. As the method for evaluating the heat resistance, theevaluations of reflow crack resistance and the temperature cycleresistance were used.

In the evaluation of the reflow crack resistance, each of the sampleswas passed through an IR reflow furnace, the temperature in which wasset to raise to the highest temperature of the sample surface 260° C.and keep the temperature for 20 seconds. The sample was then allowed tostand still at room temperature, so as to be cooled. This treatment wasrepeated 2 times. In this sample, cracks were examined with the nakedeye and an ultrasonic microscope. The case that in none of the samples,the number of which was ten, a crack was generated was judged to be good(◯). The case that in one or more of the samples, a crack was generatedwas judged to be poor (X).

About the temperature cycle resistance, the samples were allowed tostand still in an atmosphere of −55° C. temperature for 30 minutes, andthen allowed to stand still in an atmosphere of 125° C. temperature for30 minutes. This step, which was one cycle, was repeated 1000 times.After the 1000 cycles, the sample was observed with an ultrasonicmicroscope. The case that in none of the samples, the number of whichwas ten, a break such as a crack or peeling was generated was judged tobe good (◯). The case that in one or more of the samples, a break wasgenerated was judged to be poor (X).

TABLE 2 Com- Com- Com- Com- Com- para- para- para- para- para- tive tivetive tive tive Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Con- ampleample ample ample ample ample ample ample ample ample ample Items Unitditions 1 2 3 4 5 6 1 2 3 4 5 Breaking MPa 25° C. 5.8 4.6 4.4 5.5 7.45.7 19.4 1.4 7.2 2.3 2.2 strength Breaking % 25° C. 28 35 40 20 15 20330 425 145 103 100 elongation Flow μm 160° C.  660 328 790 380 50 450523 >1000 50 346 222 Remaining % — 0.4 0.3 0.4 0.4 0.3 0.4 0.4 0.4 0.40.3 0.4 volatile matter content Ad- Before Kg 260° C.  1.1 1.2 1.1 1.10.4 1.1 1.6 1.4 0.3 1 1.3 he- the sive absorption force of moistureAfter Kg 260° C.  0.8 0.7 0.7 0.7 0.3 0.8 1.5 1 0.3 0.7 1 the absorptionof moisture Elastic MPa 25° C. 10 Hz 1000 1900 720 1800 — 1300 300 — —1200 1300 modulus 60° C. 10 Hz 4.2 13 2.5 20 35 6.4 5 5 30 7 12  25° C.900 Hz 5400 7000 5800 6200 — 6600 3000 — — 3800 3600 −20° C. 10 Hz  78008000 6700 7800 — 7900 3200 — — 3900 3800 Tacking gf 25° C. 5 5 8 3 3 4 618 3 11 7 strength 40° C. 12 27 40 27 12 10 18 37 11 63 38 Air 60° C. 4162 85 55 23 32 40 67 23 96 58 face 80° C. 90 161 198 111 34 78 64 200 40176 89 Tacking gf 25° C. 8 7 9 4 4 6 11 19 4 9 9 strength 40° C. 15 3145 27 14 13 36 55 10 155 61 Substrate 60° C. 97 290 240 120 27 88 67 10234 290 302 film face 80° C. 162 300 300 173 49 142 171 300 40 300 340Laminate — 60° C. Good Good Good Good Poor Good Good Good Poor Good Goodproperty Break- — 25° C. Broken Broken Broken Broken Broken — Not NotNot Not Not ability broken broken broken broken broken Reflow — — ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ crack resistance Temperature — — ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ X ◯ ◯cycle resistance

About Examples 1 to 4, their elastic moduli, breaking strengths and thebreaking elongations are within the ranges specified in the invention,and their laminate property and breakability are good. Theirhandleability is excellent since their tacking strengths are small atroom temperature, and further their reflow crack resistance andtemperature cycle resistance are also excellent since their adhesiveforces at high temperature are excellent. About Example 5, itsbreakability is good but the laminate property at 60° C. is poor so thatExample 5 is unsuitable for low-temperature lamination. AboutComparative Examples 1 to 5, their elastic moduli, breaking strengthsand breaking elongations are out of the ranges specified in theinvention. Thus, all of them are poor in breakability.

[Production of Adhesive-Sheet-Stuck Semiconductor Chip by StealthDicing]

Each of the adhesive sheets of Examples 1 to 3, Example 6 andComparative Examples 1 and 5 was combined with appropriate one out ofthe following steps 1 to 4, thereby producing an adhesive-sheet-stucksemiconductor chip. The breakability and the forcing-out of the resinfrom its edge were evaluated. Each of the steps is roughly shown inTable 3. Table 4 shows a combination of each of the adhesive sheets witha step therefor, and evaluation results of the breakability and theforcing-out from the edge.

(Step 1)

An adhesive sheet was laminated at 60° C. onto a semiconductor wafer(thickness: 80 μm) to be diced with a hot roll laminator (Riston,manufactured by DuPont). A laser ray was radiated into the resultantadhesive-sheet-stuck semiconductor wafer A, as illustrated in FIG. 2,thereby forming modified regions inside the wafer. Next, a dicing tape((UC3004M-80) manufactured by the Furukawa Electric Co., Ltd.) wasstacked on the other face of the adhesive sheet. A ring made ofstainless steel was fitted to the periphery of the dicing tape.Subsequently, the ring was fixed thereto and the dicing tape wasexpanded with an expanding device. As for conditions for this expand,the expand speed was 30 mm/, and the expand amount was 15 mm.

(Step 2)

A laser ray was radiated into a semiconductor wafer (thickness: 80 μm),as illustrated in FIG. 2, to form modified regions inside the wafer.Next, an adhesive sheet was laminated onto the semiconductor wafer A at60° C. with a hot roll laminator (Riston, manufactured by Du Pont).Next, a dicing tape ((UC3004M-80) manufactured by the Furukawa ElectricCo., Ltd.) was stacked on the other face of the adhesive sheet. A ringmade of stainless steel was fitted to the periphery of the dicing tape.Subsequently, the ring was fixed thereto and the dicing tape wasexpanded with an expanding device. As for conditions for this expand,the expand speed was 30 mm/s, and the expand amount was 15 mm.

(Step 3)

A laser ray was radiated into a semiconductor wafer (thickness: 80 μm),as illustrated in FIG. 2, to form modified regions inside the wafer.Next, a dicing tape integrated type sheet, wherein an adhesive sheet anda dicing tape ((UC3004M-80) manufactured by the Furukawa Electric Co.,Ltd.) were laminated onto each other, was laminated onto the wafer at60° C. with a hot roll laminator (Riston manufactured by Du Pont). Aring made of stainless steel was fitted to the periphery of the dicingtape. Subsequently, the ring was fixed thereto and the dicing tape wasexpanded with an expanding device. As for conditions for this expand,the expand speed was 30 mm/s, and the expand amount was 15 mm.

(Step 4)

A laser ray was radiated into a semiconductor wafer (thickness: 80 μm),as illustrated in FIG. 2, to form modified regions inside the wafer.Next, an adhesive sheet was laminated onto the wafer at 60° C. with ahot roll laminator (Riston manufactured by Du Pont). Thereafter, theadhesive sheet was heated at 120° C. for 10 minutes. Next, a dicing tape(UC3004M-80) manufactured by the Furukawa Electric Co., Ltd.) wasstacked on the other face of the adhesive sheet. A ring made ofstainless steel was fitted to the periphery of the dicing tape.Subsequently, the ring was fixed thereto and the dicing tape wasexpanded with an expanding device. As for conditions for this expand,the expand speed was 30 mm/s, and the expand amount was 15 mm.

TABLE 3 Step 1 Preparation of a wafer ↓ Sticking of an adhesive sheet ↓Laser processing ↓ Sticking of a dicing tape ↓ Expand Step 2 Preparationof a wafer ↓ Laser processing ↓ Sticking of an adhesive sheet ↓ Stickingof a dicing tape ↓ Expand Step 3 Preparation of a wafer ↓ Laserprocessing ↓ Sticking of an adhesive sheet integrated type dicing tape ↓Expand Step 4 Preparation of a wafer ↓ Laser processing ↓ Sticking of anadhesive sheet ↓ Heating of the adhesive sheet ↓ Sticking of a dicingtape ↓ Expand

(Breakability)

After the expand, it was observed with an optical microscope whether ornot each of the semiconductor wafers and the adhesive sheet thereon werebroken. The case that the product was broken by 98% or more of thedistance over which the dicing was performed was judged to be very good(⊚); the case that the product was broken by 90% or more thereof wasjudged to be good (◯); the case that the product was broken by 50% ormore and less than 90% thereof was judged to be partially good (Δ); andthe case that the product was broken by less than 50% thereof was judgedto be poor (X)

(Forcing-Out from the Edge)

About each of the picked-up adhesive-sheet-stuck semiconductor chips,the edges of the semiconductor chip and the adhesive sheet were observedas illustrated in FIG. 10. The length 8 of the adhesive sheet forced outfrom the edge of the chip without being broken was defined as theforced-out length. The case that the length was zero or more and lessthan 20 μm was judged to be very good (⊚); the case that the length wasfrom 20 to 100 μm was judged to be good (◯); and the case that thelength was more than 100 μm was judged to be poor (X)

TABLE 4 Example Example Example Example Example Example Example ExampleItems 7 8 9 10 11 12 13 14 Adhesive sheet Example 1 Example 1 Example 1Example 1 Example 2 Example 2 Example 2 Example 2 Step Step 1 Step 2Step 3 Step 4 Step 1 Step 2 Step 3 Step 4 Breakability ⊚ ◯ ◯ ⊚ ◯ Δ Δ ⊚Forcing-out ⊚ ◯ ◯ ⊚ ◯ ◯ ◯ ⊚ from the edge Breaking strength 5.8 5.8 5.88 4.6 4.6 4.6 7.8 (Mpa) Breaking 28 28 28 6.1 35 35 35 9.5 elongation(%) Elastic 25° C. 10 Hz 1000 1000 1000 1400 1900 1900 1900 2200 modulus60° C. 10 Hz 4.2 4.2 4.2 15 13 13 13 20 (MPa)  25° C. 900 HZ 5400 54005400 6500 7000 7000 7000 7500 −20° C. 10 Hz  7800 7800 7800 7850 80008000 8000 8100 Example Example Example Example Example Example ExampleExample Items 15 16 17 18 19 20 21 22 Adhesive sheet Example 3 Example 3Example 3 Example 3 Example 6 Example 6 Example 6 Example 6 Step Step 1Step 2 Step 3 Step 4 Step 1 Step 2 Step 3 Step 4 Breakability ◯ Δ Δ ⊚ ⊚⊚ ⊚ ⊚ Forcing-out ◯ ◯ ◯ ⊚ ⊚ ⊚ ⊚ ⊚ from the edge Breaking strength 4.44.4 4.4 7.8 5.7 5.7 5.7 8 (Mpa) Breaking 40 40 40 12 20 20 20 6.4elongation (%) Elastic 25° C. 10 Hz 720 720 720 1200 1300 1300 1300 1600modulus 60° C. 10 Hz 2.5 2.5 2.5 12 6.4 6.4 6.4 15 (MPa)  25° C. 900 Hz5800 5800 5800 6800 6600 6600 6600 7500 −20° C. 10 Hz  6700 6700 67007500 7900 7900 7900 8200 Comparative Comparative Comparative ComparativeItems Example 6 Example 7 Example 8 Example 9 Adhesive sheet ComparativeComparative Comparative Comparative Example 1 Example 5 Example 1Example 5 Step Step 1 Step 2 Step 3 Step 4 Breakability X X X XForcing-out X X X X from the edge Breaking strength 19.4 2.2 19.4 2.2(Mpa) Breaking 330 100 330 100 elongation (%) Elastic 25° C. 10 Hz 3001300 300 1300 modulus 60° C. 10 Hz 5 12 5 12 (MPa)  25° C. 900 HZ 30003600 3000 3600 −20° C. 10 Hz  3200 1800 3200 1800

About Examples 7 to 22, their elastic moduli, breaking strengths and thebreaking elongations are within the ranges specified in the presentinvention, and their laminate property and breakability are good. Theirhandleability is excellent since their tacking strengths are small atroom temperature, and further their reflow crack resistance andtemperature cycle resistance are also excellent since their adhesiveforces at high temperature are excellent. In particular, in Examples 10,14, 18 and 22, the breakability thereof is improved since the adhesivesheets therein were post-heated. Examples 19 to 22, wherein the breakingelongations of the adhesive sheets were decreased, have excellentbreakability.

About the Comparative Examples, their elastic moduli, breaking strengthsand breaking elongations are out of the ranges specified in the presentinvention. Thus, all of them are poor in breakability.

According to the present invention, it is possible to provide anadhesive sheet which can be stuck onto a wafer at a low temperature of100° C. or lower, is as flexible as the sheet can be handled at roomtemperature, and can be cut at the same time as the wafer is cut underordinary cutting conditions.

According to the adhesive sheet of the present invention, it is alsopossible to apply the following methods simultaneously to a dicing stepin the production of a semiconductor device: a wafer-cutting method suchas half cut dicing or stealth dicing; and a method of using an adhesivesheet in a wafer-back-face sticking mode. For this reason, the dicingstep can be effectively attained.

Even when a very thin wafer having a thickness of 100 μm or less isused, the use of the adhesive sheet of the invention makes itunnecessary to cut the wafer and the adhesive sheet simultaneously witha dicing saw or the like; therefore, the speed of the dicing can be madelarge. For this reason, according to the adhesive sheet of theinvention, the processing speed of semiconductor devices and the yieldthereof can be improved.

When the adhesive sheet of the invention is used, cut faces of theadhesive sheet and a chip thereon can be made consistent with each otherwithin the range of a difference of 100 μm or less. Even if the cuttingis not attained, it can easily be checked whether the adhesive sheet isseparated or not; therefore, picking-up failure is not caused and asemiconductor device can be effectively produced.

Moreover, bonding reliability is excellent in the step of jointing asemiconductor element with a semiconductor-element-mounting supportmember in the production of a semiconductor device, as well. In otherwords, when a semiconductor element is mounted onto a support member,the adhesive sheet of the invention has necessary heat resistance andhumidity resistance and exhibits satisfactory workability.

Those skilled in the art will understand that the above are concernedwith preferred embodiments of the present invention and a great numberof changes and modifications can be carried out without disobeying thespirit and scope of the invention.

1. An adhesive sheet having a property that it can be laminated togetherwith dicing tape onto a wafer prior to stealth dicing, and is capable ofbeing subjected to stealth dicing, and which comprises: a polymercomponent, which includes acrylic rubber having a glass transitiontemperature of −30° to 50° C., and a weight-average molecular weight of50,000 to 1,000,000; and a filler, wherein the breaking strength of theadhesive sheet in a B-stage state is from 0.1 to 10 MPa at 25° C., andthe breaking elongation thereof being from 1 to 40% at 25° C.
 2. Theadhesive sheet according to claim 1, wherein the elastic modulus of theadhesive sheet in a B-stage state is from 1 to 3000 MPa in measurementof the dynamic viscoelasticity at 25° C. and 10 Hz, and the elasticmodulus thereof being from 4000 to 20000 MPa in measurement of thedynamic viscoelasticity at 25° C. and 900 Hz.
 3. The adhesive sheetaccording to claim 1, wherein the elastic modulus of the adhesive sheetin a B-stage state is from 1 to 3000 MPa in measurement of the dynamicviscoelasticity at 25° C. and 10 Hz, and the elastic modulus thereofbeing from 4000 to 20000 MPa in measurement of the dynamicviscoelasticity at −20° C. and 10 Hz.
 4. The adhesive sheet according toclaim 1, wherein the elastic modulus of the adhesive sheet in a B-stagestate is from 0.1 to 20 MPa in measurement of the dynamicviscoelasticity at 60° C. and 10 Hz.
 5. The adhesive sheet according toclaim 1, wherein the acrylic rubber is contained in an amount of 50% orless of the total weight of the adhesive sheet from which the weight ofa filler is removed.
 6. The adhesive sheet according to claim 1, whereinthe content of remaining volatile matters is from 0.01 to 3% by weight.7. The adhesive sheet according to claim 1, which has a film thicknessof 1 to 250 μm.
 8. The adhesive sheet according to claim 1, wherein thefiller is contained in an amount of 5 to 70% of the total weight of theadhesive sheet.
 9. The adhesive sheet according to claim 1, wherein thefiller is contained in an amount of 35% to 60% of the total weight ofthe adhesive sheet.
 10. The adhesive sheet according to claim 1, whereinthe acrylic rubber is contained in an amount of 35% or less of the totalweight of the adhesive sheet from which the weight of a filler isremoved.
 11. The adhesive sheet according to claim 10, wherein theacrylic rubber is contained in an amount of from 25% to 35% of the totalweight of the adhesive sheet from which the weight of the filler isremoved.
 12. The adhesive sheet according to claim 1, wherein thepolymer component further includes epoxy resin.
 13. The adhesive sheetaccording to claim 1, laminated together with the dicing tape onto thewafer, prior to the stealth dicing.